The present invention relates generally to wet wells for the containment of materials, such as water and/or other compositions therein, e.g., underground wet wells for water or waste.
Various configurations of wet wells are available and have been used in a variety of applications. For example, as shown in FIG. 1, fiberglass wet wells available from Xerxes Corp. (Minneapolis, Minn.) may be used in wastewater applications. Such applications may include the use of an underground fiberglass wastewater tank 10, fluidly coupled to an underground wet well 20 by one or more different components 34. For example, such connection components 34 may include a nozzle 32 associated with the tank 10, a connector 38, and a nozzle 36 associated with the wet well 20. Further, as shown in FIG. 1, access to the tank 10 is provided via sump 40, manway 42, and cover 44. A vent 46 is also provided for the tank 10. Access to the interior of the wet well 20 is provided at ground surface via a cover structure 50 and a pump and conduit assembly 54 is configured for moving compositions out of the wet well 20. Such compositions (e.g., water, wastewater, etc.) generally are provided into the wet well 20 from the tank 10.
Yet further, the wet well 20 includes an anti-flotation flange 28. The anti-flotation flange 28 is a full or partial disk that surrounds the base, and extends a few inches out from the base, beyond the normal “diameter” of ribs 26. When properly buried, the flange 28 engages the surrounding burial material, and resists the tendency of the wet well 20 to “lift” or “float” under the influence of water, where the water-table or other conditions are such that the hole in which the wet well 20 is buried becomes filled or partially filled with water.
Wet wells are typically sunk vertically, or in a vertical alignment, into the ground 14, and are used to contain water, or other liquids (e.g., waste). For example, the top of the wet well 20 may be installed level with a black top material 16. Wet wells may, for example, be used in waste water facilities (e.g., such as shown in FIG. 1), in fire suppression systems, and/or in other fluid or water recovery systems (e.g., lift station and pump vault applications). A conventional wet well may be made in a variety of diameters and depths, and may be prepared in sections.
Early wet wells were prepared of wood and/or concrete materials. These materials, which typically have to be erected in situ, may present a variety of problems, most particularly involving leakage. Wet wells were subsequently prepared using steel, or steel and concrete. Steel, however, presented problems associated with corrosion. Given the nature of the contained liquids held in wet wells and other storage tanks (e.g., which include industrial wastes, organic wastes or sewage, and/or other various compositions), corrosion and subsequent leakage in such configurations present significant problems.
In comparison, fiberglass reinforced plastic (FRP) is relatively light, can be prepared at the plant and shipped to the site, and is corrosion resistant. It is similarly unlikely to develop leaks. As such, wet wells (e.g., underground wet wells) have been made using FRP to provide watertight and rustproof construction. For example, a FRP wet well may be made on a male mold or mandrel, and once cured, at least preliminarily, removed from the mandrel. The process of manufacturing on a mandrel of this type is typically referred to as a “spray up” process, where fibers and plastic resin are applied over a release agent to the mandrel, which lends the wet well its shape.
To provide a FRP wet well, such as wet well 20 shown in FIG. 1, with sufficient stiffness and strength to resist applied forces, and to resist deformation or buckling, ribs 26 as shown in FIG. 1 are used. Such ribs 26 provide the molded product with hoop strength.
In a male molding process, the ribs 26 are provided by attaching a form to the molded wet well, and then laying fiber up and across the form, providing the connection between the rib and the well in the form of a secondary attachment. Processes for the manufacture of wet wells of this type are not substantially different from the processes of manufacturing underground storage tanks through the same method, such as those shown in U.S. Pat. No. 3,925,132, incorporated herein by reference.
FRP wet wells have also been prepared from plastic resin and chopped fiber that is sprayed onto the interior of a female mold. The resin is preferably applied with a catalyst, as it is sprayed together with the chopped fiber, to create a strong, relatively stiff, water impermeable and corrosion resistant wall. The mold itself includes ribs where necessary, so that they become part of the integral structure. Information on the method of comminuting the glass fibers, as well as application of the fibers and resin to the interior of the female mold, is set forth in U.S. Pat. No. 5,645,231, incorporated herein by reference. After preliminary curing, the female mold halves separate along a longitudinal axis and a full cure commences of the resin impregnating the fibrous body.
Typically in a wet well, pumps and the associated lines and valves are disposed either in the bottom of the wet well itself, or adjacent to the wet well in a separate installation. Particularly, where the pump and associated piping are to be disposed on the bottom of the wet well itself, it is necessary to provide a bottom structure that exhibits very small deflections when forces are applied thereto (e.g., upward forces on the bottom of the wet well, such as a result of water thereunder). Resistance to deflection is important even when no fluid is present in the wet well itself, such as in a situation where water surrounds the outside of the wet well (e.g., in a high-water table environment). Very limited deflection is tolerated, and excessive movement of the bottom in response to applied pressure could disrupt or break the pumps, piping and/or pumping controls, leading to pumping failure and/or leakage.
Various techniques have been used to install wet wells to provide resistance to such deflection. For example, wet wells have been installed on poured concrete structures (e.g., having a planar top surface) to prevent deflection. In other words, concrete structures, made thick enough, have been used in an attempt to provide resistance to applied forces and prevent significant deflection to the bottom of the wet well. However, the presence of cracks, or pores in the concrete, introduce leakage issues and allow fluid access to the bottom of the wet well. As such, concrete structures are not always successful to prevent deflection of the bottom of the wet well.
In other words, water can get between the concrete pad and the bottom of the wet well presenting the same applied pressure and deflection issues as if there were no concrete base provided. While one can resist the tendency of the bottom of the wet well to “float” off the base, by bolting the floor or the wet well to the concrete, the bolt holes provide leakage spots and the bolts represent points of corrosion, creating a variety of issues involving sealants. Further, others have attempted to connect the wet well bottom to the concrete slab using external anchors (e.g., extending from the bottom of the wet well) encompassed by the concrete of the pad when formed.
The concrete or the bottom of the wet well could be coated to provide a seal between the concrete and the wet well bottom in an attempt to resist leakage and fluid from reaching the bottom of the wet well. However, the applied pressures or force may frequently pop off or crack such coatings. Further, attempting to adhere the concrete base to the bottom of the wet well is both time consuming and expensive, and presents the prospect of introducing other poisons or toxins into the environment. In particular, it has proven difficult to provide a complete and lasting seal, between the concrete and the side walls, or bottom, of the wet well.
Still further, the thickness of the FRP bottom can be increased to prevent deflection thereof. For example, FRP laminates have become a preferred material because they combine significant stiffness and strength, and reduce or eliminate leakage, while also reducing the problem of corrosion. However, as the diameter of required wet wells increase, the amount of material necessary to provide FRP wet wells with sufficiently stiff bottoms that can support pumping apparatus and the like also increases, making such a solution cost prohibitive.